Category: General Article
Saturday, August 29, 2015
Submitted by Rachel Teasdale
Summary: Rachel summarizes the successes and challenges of the Axial Seamount Eruption Response expedition… and the next steps for all the scientists involved.
As the Axial Seamount 2015 Expedition comes to an end, the science team aboard the R/V Thompson is thrilled with the extensive work completed since departing Seattle on August 14. Chief Scientist Bill Chadwick was able to work around the three days of bad weather that prevented the launch of ROV Jason and AUV Sentry, and with creative rescheduling, efficient ROV Jason and AUV Sentry operations and flexibilty of the R/V Thompson crew we were able to collect the data from all pre-planned sites that were needed to accomplish the three main goals of the cruise:
1. Make seafloor pressure measurements to measure volcanic inflation/deflation.
2. Complete Incubator experiments and collect samples of hydrothermal vent fluids for chemical and microbial analyses.
3. Explore the volcano to observe, sample and document the physical and biological impacts of the April 2015 eruption including new lava flows, ash, hydrothermal plumes, and micobial oraganisms.
Bill Chadwick and Scott Nooner are both happy with the pressure dives (J2-823 and J2-824) during which a mobile pressure recorder (MPR) on ROV Jason collected data at 10 benchmarks. Bill said this data, and data from the bottom pressure recorders (BPRs; installed two years ago and recovered during this expedition), are all of very high quality. Scott loves to process the data and is already starting to make corrections such as tidal influence so he and Bill can start to consider inflation rates since the April 2015 eruption in their ongoing work to characterize the movement of magma beneath the volcano. Matt Fowler was able to get the BPRs turned-around from instrument recovery to downloading data and installing new batteries, to re-deploying them back to the seafloor, to continue monitoring the inflation and deflation of the volcano. Glenn Sasagawa’s work with the self-calibrating pressure recorder (SCPR) will continue once he’s back at Scripps Institution of Oceanography, where he will process the data the SCPR collected for the last two years, and also work on improving the instrument and its ability to survive at the ocean floor for future deployments.
The CTD casts were a success, with four vertical casts and four tow-yo casts over known vents as well as over the 2015 lava flows where new vents might occur. CTD data and samples will be analyzed at University of Washington by Nathan Buck and Rachel Spietz and other colleagues back on shore. Nathan’s CTD water samples will be used to characterize the plume in terms of Helium (He) isotopes, metals, methane and dissolved ionic compounds. Rachel will focus on the microbes that live in the water column just above the hydrothermal plumes. Analyses of proteins in the plume will help her characterize the metabolic processes of the microbial organisms. Dave Butterfield looks forward to learning the results of Nathan and Rachel’s analyses because the new plume locations and compositions are not obviously directly linked to new lava flows, but he says the complexity of trying to interpret the plumes is part of what makes science challenging, exciting, and keeps him coming back to Axial Seamount year after year.
The remote access sampler (RAS; see image above right) that was set up by Kevin Roe, will collect samples approximately once a week for the next year when the samples will be retrieved. RAS data will help Dave and Kevin understand the longevity of the hydrothermal vents as well. Much of Dave and Kevin’s work was also aimed at the sampling of vent fluids during the Jason dives.
Dave Butterfield attributes much of the success of the incubator to the hard work of Ryan Wells and Ben Larson in engineering and preparing the incubator to collect and analyze samples on the seafloor. Once the incubators were back on board, Ben collected gas from each sample, then the microbiology group extracted their samples for experiments that parallel those completed in the incubator on the ocean floor. Emily Reddington and Chris Algar filtered hydrothermal vent samples over pre-determined time periods, just as was done in the incubator. Microbes collected on filters of both sample sets will be analyzed once back at the Marine Biological Lab in Woods Hole, Massachusetts. Chris acknowledges that there is still a lot of lab work to be completed, but is excited to learn the results of analyses started here on the ship.
Graduate student Begum Topçuoğlu and her advisor, Jim Holden have also processed microbes from hydrothermal vent fluids, and are pleased with the number and quality of samples they were able to collect while at sea. On board, they successfully cultured thermophilic (organisms that live in approximately 55°C water) and hyperthermophilic (live above 80°C) organisms, some of which are methanogens (they produce methane) and others produce sulfur. Begum has numerous analyses to complete once back in the lab, but she and Jim are excited to learn the results of the parallel incubator experiments, which Begum calls revolutionary in terms of learning more about sampling microbes in the high pressure environment of the ocean floor.
In addition to originally planned research at Axial Seamount, the 2015 expedition became unexpectedly well-timed for exploring the geological, chemical and biological effects of the April 2015 eruption. As noted in previous blogs, a variety of flow morphologies were observed on the 2015 flows and expert piloting of the ROV Jason facilitated the collection of nearly 30 rock samples from the 2015 lava flows. In addition, a sample of ash was “slurped” from the surface of one of the pressure campaign benchmarks. Jenny Paduan has prepared the samples for further chemical analyses to help characterize the lavas in terms of compositional variations with previous eruptions, which will provide a larger idea of the chemical processes of the magma at depth.
Exploration of the lava flows was facilitated by maps generated by AUV Sentry missions in and around the caldera. High resolution maps processed from AUV data have already revealed details of the lava flows such as channels that have been filled in with 2015 flows and collapse features. Multibeam surveys also discovered new areas covered with 2015 lava that were previously unknown on the NE rim of the caldera. No fissures that would have fed the flows have been identified thus far, but that area will likely be targeted for wider surveys in future expeditions. Multibeam maps will also be used to better understand the inflation and deflation of Axial Seamount in the future because the vertical movements of the seafloor are large enough to detect by repeated surveys. These data are yet another significant contribution to understanding the most recent eruption as well as the dynamics of this very active submarine volcano.
Images courtesy of the 2015 Axial Team.